Anisotropic excitonic photocurrent in $\beta$-Ga${}_2$O${}_3$

Abstract

Polarization dependent photocurrent spectra are measured on a (001) $\beta$-Ga${}_2$O${}_3$ Schottky photodetector, where the linear polarization of light is rotated within the ab plane. Three spectral peaks at 4.92 eV, 5.15 eV, and 5.44 eV are observed that vary in intensity with the optical polarization direction. The peak transition energies are consistent with excitons previously reported in $\beta$-Ga${}_2$O${}_3$ due to interband transitions modified by the valence band p-orbital anisotropy and the electron-hole Coulombic attraction. The measured polarization-dependence of the photocurrent matches our predictions based on electromagnetic simulations of anisotropic absorption using the complex dielectric function tensor extracted from previous ellipsometry studies. These results illustrate the dominance of excitonic absorption and photocurrent in $\beta$-Ga${}_2$O${}_3$ both below and above the band gap, demonstrate a combined theoretical/experimental understanding of anisotropic photocarrier generation, and validate previous atomistic band structure calculations in this low-symmetry ultra-wide band gap semiconductor.

arXiv comment15 pages, 1 table, and 4 figure

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Cited by in corpus (2)

• The anisotropic Beer-Lambert law in $\beta$-Ga${}_2$O${}_3$: Spectral and polarization dependent absorption and photoresponsivity
• Origin of the Anisotropic Beer-Lambert Law from Dichroism and Birefringence in $\beta$-Ga${}_2$O${}_3$